Large eddy simulation and laser diagnostic studies on a low swirl stratified premixed flame
Journal article, 2009
This paper presents numerical simulations and laser diagnostic experiments of a swirling lean premixed
methane/air flame with an aim to compare different Large Eddy Simulations (LES) models for reactive
flows. An atmospheric-pressure laboratory swirl burner has been developed wherein lean premixed
methane/air is injected in an unconfined low-speed flow of air. The flame is stabilized above the burner
rim in a moderate swirl flow, triggering weak vortex breakdown in the downstream direction. Both
stereoscopic (3-component) PIV and 2-component PIV are used to investigate the flow. Filtered Rayleigh
scattering is used to examine the temperature field in the leading flame front. Acetone-Planar Laser
Induced Fluorescence (PLIF) is applied to examine the fuel distribution. The experimental data are used to
assess two different LES models; one based on level-set G-equation and flamelet chemistry, and the other
based on finite rate chemistry with reduced kinetics. The two LES models treat the chemistry differently,
which results in different predictions of the flame dynamic behavior and statistics. Yet, great similarity
of flame structures was predicted by both models. The LES and experimental data reveal several intrinsic
features of the low swirl flame such as the W-shape at the leading front, the highly wrinkled fronts in
the shear layers, and the existence of extinction holes in the trailing edge of the flame. The effect of
combustion models, the numerical solvers and boundary conditions on the flame and flow predictions
was systematically examined.